Meeting Abstract

97.7  Wednesday, Jan. 7  Condensation onto the skin as a means of water gain by tree frogs in tropical Australia. TRACY, C.R.*; BETTS, G.; CHRISTIAN, K.A; Charles Darwin University; Charles Darwin University; Charles Darwin University chris.tracy@cdu.edu.au

The savannas of tropical northern Australia present a challenge for frogs attempting to maintain water balance because there is often no free water available for several months during the dry season. However, green tree frogs (Litoria caerulea, Hylidae) can be found active during the cool dry season despite the fact that free water is not available and environmental temperatures can be as cool as the critical minimum temperature for this species (11 &degC). We hypothesized that dry season activity may reflect a strategy to obtain water by being active in cool conditions and having condensation form on the body when frogs return to a warm, humid tree hollow. Therefore, we measured the mass gained when a tree frog moves from a cool outside environment into a tree hollow, using both a natural hollow, and a simulated hollow in the laboratory. Even with a relatively small temperature difference between frog body temperature and air temperature in the hollow, frogs gained mass. With a large (15 &degC) difference in temperature, frogs were able to gain about 0.5% of their body mass in water condensed onto their skin. In areas with extended periods with no access to free water, even small gains in water would be advantageous to frogs, thus the use of condensation as a means of water gain may be a significant source of water uptake.